Flight timer and retractable landing gear for model airplanes



May 8, 1951 D. w. CAMERON FLIGHT TIMER AND RETRACTABLE LANDING GEAR FOR MODEL AIRPLANES Filed-Jan. 9, 1945 2 Sheets-Sheet l INVENTOR. DONALD W CAMERON ATTORNEYS May 8, 1951 D. w. CAMERON ,788

FLIGHT TIMER AND RETRACTABLE LANDING GEAR FOR MODEL AIRPLANES Filed Jan. 9, 1945 2 Sheets-Sheet 2 A I 24 w 5 I 6 INVENTOR.

DONALD n4 CAM20N Patented May 8, 1951 UNITED STATES PATENT OFFlCE FLIGHT TIMER AND RETRACTABLE LAND- ING GEAR FOR MODEL AIRPLANES Donald William Cameron, Chino, Calif.

Application January 9, 1945, Serial No. 572,040

5 Claims. 1

This invention. relates to a combined flight timer and rctractible landing gear for model airplanes.

An object of the invention is to provide an improved timer mechanism which will open the ignition c'-'cuit for the internal combustion engine of the model airplane after a predetermined length of time so as to discontinue its operation and which will also release a retracticle landing gear for the model airplane so that will automatically be swung into its retracted. position shortly after the take-off. in odel airplane contests a landing gear of some type is normally required although it is not required that landing gear remain in extended p on ht or during landing of the plane. the improved construction it is proposed to have a retractible landing in extended position at the time of take-o. quickly moved into retracted po ion af it will not hinder or slow the plane. A timer mechanism usually in the form or" an adjustable clashpot controls the length of time tha the plane is operated. in accordance with the present in ention the dashpot performs both functions, to t. opening the switch that controls the ignition circuit of the engine and releases the landing gear so that it may swung into retracted position. The release the gear of course normally takes place Well in ad- Vance of the time that the engine of the plane is shut off.

Another object of the invention is to provide an improved dashpot which can be easily and economically constructed and which may be accurately adjusted to vary the length of time that the engine remains in operation.

Another object of the invention is to provide a dashpot for timers of model airplanes wherein leakage around the needle valve controlling the speed of operation of the dashpot is effectively prevented and adjustment of the needle valve may be accurately maintained despite the vibration to which it may be subjected.

Still further object of the invention to provide an improved switch operable by the dashpot that controls the igni lion circuit or the engine.

With the foregoing and other objects in view, which will be made manifest in the follm tailed description and specifically pointed. the appended claims, reference is had to the accompanying drawings for an illustrative ment of the invention, wherein:

Figure 1 is a View in side elevation of a airplane illustrating the construction embodying e-off so that the present invention as having been installed therein;

Fig. 2 is a view in side elevation, parts being broken away shown in vertical section illustrating the operating parts of the flight timer and retractible landing gear;

Fig. 3 is a view in front elevation of the apparatus illustrated in Fig. 2;

Fig. i is a sectional view taken substantially upon the line -'ll upon Fig. '3;

Fig. 5 is a view in side elevation of the dashpot illustrating portions thereof in vertical section taken substantially upon the line 5-5 upon Fig. 3; and

G is a partial section taken substantially upon the lineS-fi upon Fig. 5.

Referring to the accompanying drawings .rein similar reference characters designate similar parts throughout, it indicates a model airplane, the pro, ler ii of which is driven by a miniature gasoline motor 2. The flight timer embodying the present invention comprises a 'dashpot having a cylinder i3 Within which is a piston i l urged to one end of the cylinder by a compression spring i5. The piston has a stem or red iii carrying a handle ll. When the handle s is pulled forwardly the compression spring 5 compressed and air is taken into the cylinder around the flange of the cup leather on the piston. On release of the handle I! the spring i5 is effective to urge the piston totvard'the rear end of the cylinder. Air in the cylinder escapes through an outlet 58 which is controlled by an adjustable needle valve the needle of which is indicated at H).

A feature of the invention resides in the c0nstruction of the dashpot cylinder so that leakage through the outlet is effectively prevented and the speed of operation of the dashpot can consequently be accurately adjusted and controlled by the needle valve. To this end, I prefer to cast the cylinder 13 of plastic and to form a boss or protuberance on one side as indicated at 2*? Within which there is disposed a metal insert 2!. T is metal insert may have a vertical core therethrough as illustrate in Fig. '5, the upper end of which is threaded complementary to the threads 22 on the stem 23 of the needle The insert is preferably cast or molded n. the plastic at the that the dashpot cy"nder is formed so that the plastic being formed directly around the insert forms a leakp cof joint therewith thrc-u h ut its length. Thereafter, a hole is drilled rad lily of the cylintier it through the protuberance 2G and the intact 39.

sert that communicates with the central bore 2d of the insert and forms the outlet 58. By thus constructing the dashpot leakage around the insert is effectively prevented and the escape of air through the outlet 58 may be accurately controlled by the adjustment of the needle valve. On the forward end of the cylinder i3 there is an aperture 25 within which is rotatably disposed. the base of a knurled handle 26 on the stem 23. Intermediate the aperture 25 and the protuberance 28 there is a spring This spring may have parallel slits defining opposed portions 28 and 29 which bear against opposite sides of the stem 23. The ends of the spring bear against the sides of the cylinder i3 and serve to impose a lateral pressure on the stem 23 to hold it frictionally in any adjusted position. In this manner when the needle valve has been adjusted to regulate the rate of return of the piston i i the adjustment may be maintained despite the vibration to which the device may be On the forward end of cylinder 53 there is mounted a switch. This switch may be located on a cap or closure 36 that closes the forward end of the cylinder and which is preferably formed of plastic. in this closure there may be a central grommet 3i through which the stem or piston rod H3 slidably extends. On opposite sides of this grommet there are two upstanding bosses 32 and 33 which have rearwardly facing forward shoulders 34 and 55. The shoulders 35 limit forward movement of a main switch element 35 anchored on one end on a stem 37 on cap 30. This main switch element carries at its opposite end a contact 38 which with its oompanion contact 39 are in circuit with the ignition apparatus of the engine i2.

A feature of the invention is to have the switch possess a snapover action so that when it is operated by the dashpot it will positively and. sharply open the ignition circuit. To this end the main switch element 38 has a relatively wide slot 49 formed therein designed to accom- 'moclate a secondary switch element ll, the forward movement of which is limited by the shoulders 34. This switch element has one end seated on the standard 3? so that it may swing from the full line position shown in Fig. 2 to the dotted line position shown therein. The other end of the secondary switch element is engaged by a compression spring t2 which is compressed between the upper end of the secondary switch element and the upper end of the slot iii. This spring is consequently effective to press the secondary switch element against the standard 3'! at all times and to urge it into either of the two positions shown in Fig. 2. When the spring is in the full line position shown in Fig. 2, the effect of its compression is to urge the main switch element 36 into a position wherein its contact 38 is pressed firmly against its companion con- I-Iowever, if the secondary switch element 4! is pressed through the slot it so that the spring will snap over and assume the position shown in dotted lines in Fig. 2, the reaction of the spring is to urge the main switch element into the position shown in Fig. 4, wherein the contacts 38 and 39 are disengaged.

When the handle it is pulled forwardly its maximum distance the piston may engage the lower end of the grommet 3i and lift or slide the grommet into engagement with the secondary switch element ti thus returning it to the full line position shown in Fig. 2, wherein the contacts 38 and 39 are closed. On release of I bent upwardly portions 6! the handle I! spring I5 is effective to slowly return the piston to the rear end of the cylinder I3 and as it approaches the end of its stroke the hub it of a knurled nut threaded onto the stem it engages the secondary switch element 4| and shifts it over center with relation to the main switch element 35, thus opening the ignition circuit for the engine after a predetermined length of time which is governed by the adjustment of the needle valve l9.

Associated with the timer is the support for a retractible landing gear. This consists of a bracket 46 having spaced arms 41 and 48. A strut 49 on which is rotatably mounted a wheel 50 carries a bracket M with cars 52 that are pivoted to the spaced arms 41 and 4B. The upper portion of the strut provides a pin 53 receivable in an aperture in one end of an angular lever 54. This lever is pivotally mounted between the arms t! and 48 of bracket 46, such as by ears 55. A tension spring 56 is connected to the strut 39 below its pivot so as to normally urge the landing gear into the dotted line position shown in Fig. 2. The spring has suflicient potential energy when in full line position, as shown in Fig. 1, to raise the landing gear by itself. The upper end of the tension spring is connected to the angular lever 54 above its pivotal connection with bracket '36 so as to urge the angular lever into the full line position shown in Fig. 2, wherein it is in engagement with the pin 53 on the strut. When the strut is in its elevated position, downward movement of the horizontal portion of lever 54 is limited by engagement of its stops L ia with the bracket 45. The upper end of angular lever 5A is engageable by the flange portion of the knurled nut 44.

As a convenient means of construction the contact 39 is mounted on a strip of sheet metal 5'! which rests upon the cap as between two opposed bosses 58 and 59. The side edges of this plate have extensions 66 which bear against the sides of the bosses to prevent lateral displacement. Intermediate these extensions there are forming springs which bear on shoulders 62 on the bosses. The shoulders 63 on these bosses are vertically substantially even with the shoulders 35 and limit upward movement of the main switch element 35. This form of construction facilitates manufacture and assembly and will position the contact properly on the cap so as to be engageable by contact 38.

The operation of the above-described construction is as follows: Assuming that the needle valve l9 has been adjusted to properly regulate the action of the dashpot on rearward movement of the piston the switch may be closed as previously described. When the angular lever 54 is released the spring 5% urges it into the full line position shown in Fig. 2, and while in this position the strut may be swung relatively to bracket 46 to occupy the full line position shown in Fig. 2, wherein the pin 53 is engaged by the lever 54 which constitutes a latch. On release of handle I? piston Hi slowly progresses rearwardly in cylinder l3 and during its travel nut i l will engage the upper end of lever 56. When the lever 54 is thus engaged and swung into the dotted line position shown in Fig. 2, the pin 53 is disengaged'and spring 56 is effective to swing the landing gear into its retracted position illustrated in Fig. 2, in dotted lines. This will ordinarily occur shortly after the take-off so that the landing gear will not impede or retard flight. Ultimately the hub on nut 44 will engage the secondary switch element 4! and cause it to snap into the dotted line position shown in Fig. 2 thereby moving contact 38 to the left as the parts are depicted in Fig. 2, causing the contacts 38 and 39 to disengage. This opens the ignition circuit to the engine and causes its operation to discontinue thus allowing the plane to descend.

From the above-described construction it will be appreciated that the improved timer is highly advantageous in that by the construction of the cylinder 13 leakage through the outlet incapable of being controlled by the needle valve 19 is effectively prevented. Consequently, the needle valve by adjustment may properly and accurately regulate the operation of the dashpot. During the operation of the dashpot the landing gear may be automatically retracted and ultimately the ignition circuit of the engine may be definitely and positively opened.

Various changes may be made in the details of construction without departing from the spirit and scope of the invention as defined by the appended claims.

I claim:

1. In combination, a model airplane, a landing gear pivotally mounted thereon, spring means urging the landing gear into retracted position, latching means for holding the landing gear in extended position, a dashpot, a switch controlling the continued operation of the airplane, and means operable by the dashpot for causing the latch to release the landing gear and open the switch.

2. In combination, a model airplane, a landing gear pivotally mounted thereon, spring means urging the landing gear into retracted position, said spring means being capable of retracting the landing gear, latching means for holding the landing gear in extended position, a dashpot, and means operable by the dashpot for causing the latch to release the landing gear and enable it to be swung into retracted position.

3. In combination, a model airplane, a retractible landing gear for the airplane, potential energy means connected to the landing gear hav ing sufiicient potential energy to retract the landing gear, means to prevent the landing gear from being retracted, and other means for rendering the last named means inoperative to permit the potential energy means to release its energy and retract the landing gear.

4. In combination, a model airplane, a landing gear foldably mounted thereon, resilient means urging the landing gear into retracted position, means opposing the resilient means for preventing the resilient means from retracting the landing gear, dashpot means, switch means controlling the continued operation of the airplane, and means operable by the dashpot means for causing the second named means to be rendered inoperative so that the landing gear will be retracted and for opening the switch.

5. In combination, a model airplane, a landing gear foldably mounted therewith, resilient means urging the landing gear into retracted position, the resilient means being the sole means for retracting the landing gear, means opposing the resilient means for preventing the resilient means from retracting the landing gear, dashpot means, switch means controlling the continued operation of the airplane, and means operable by the dashpot means for causing the means opposing the resilient means to be rendered inoperative so that the landing gear will be retracted and for opening the switch.

DONALD WILLIAM CAMERON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 758,020 Robinson Apr. 19, 1904 1,457,328 VanBerkel June 5, 1923 1,843,597 Cofiman Feb. 2, 1932 2,207,189 Austin et al. July 9, 1940 2,240,892 Meyer et a1 May 6, 1941 2,292,416 Walker Aug. 11, 1942 

